WASHINGTON — For the past several weeks, Herman Cain has been basking in the attention that comes with being the unlikely, unexpected front-runner in a topsy-turvy race for the Republican presidential nomination.

On Monday, the self-styled “Washington outsider” got a glimpse of the dark side of sudden scrutiny as he was dogged by questions in the U.S. capital about allegations he sexually harassed two women in the 1990s and paid a cash settlement to both of them.

“I have never sexually harassed anyone and those accusations are totally false,” Cain said to a packed crowd at the National Press Club in response to a Politico.com story about the accusations levelled against him when he was head of the National Restaurant Association in the 1990s.

“It was concluded after a thorough investigation that it had no basis,” the one-time pizza magnate said, referring to the accusations as a “witch hunt.”

He added he was unaware of any settlement paid to the women, who left their jobs at the organization because of Cain’s inappropriate behaviour, according to Politico.

“I hope it wasn’t for much, because I didn’t do anything,” Cain said.

It was a relatively unusual day on the hot seat for the 65-year-old Georgia businessman, who’s also facing allegations that two of his top campaign workers started up a tax-exempt charity in Wisconsin to fund his presidential bid in its infancy earlier this year. Such a corporation violates federal election laws.

Cain said he wasn’t aware of the allegations and added his campaign was looking into it.

The glare of negative publicity comes following Cain’s meteoric rise in the polls that currently has him running neck and neck with Mitt Romney, the former governor of Massachusetts who’s been the front-runner in the race for months.

A new poll released Monday by the University of Texas and the Texas Tribune even has Cain leading Texas Gov. Rick Perry among Republicans in the Lone Star state.

The survey, the latest of several showing Cain on top, served as a reminder: the Georgia businessman is managing to surpass marquee candidates like Romney and Perry despite their deep pockets and large political staffs in key primary states. Cain, as of yet, possesses neither.

“As a result of today’s big news story, I really know what it feels like to be No. 1,” Cain said to big laughs as he took to the podium at the National Press Club.

There’s little doubt his sudden popularity is earning him some enemies. The conservative punditry has blamed the “liberal media” for the spate of bad news stories on Cain, apparently forgetting the media’s treatment of philandering Democrats like Bill Clinton and John Edwards.

“Liberals are terrified of Herman Cain,” right-wing agitator Ann Coulter said of the sexual harassment allegations, calling them a “high-tech lynching.”

“He is a strong, conservative black man…. They are terrified of strong, conservative black men,” she said on Fox News.

One former Republican front-runner, however, said the calls are likely coming from inside the house.

Mike Huckabee, the former governor of Arkansas who came close to winning the nomination in 2008, told a conservative radio host he could “almost guarantee” that another Republican campaign leaked the sexual harassment information to Politico.

He said he was subjected to similar tactics in 2008, accusing other campaigns of hiring investigators to dig through his garbage and show up at his children’s elementary schools pretending to be federal inspectors.

“It’s insane. One of the fundamental things a candidate will spend money on is (opposition) research,” Huckabee told Laura Ingraham.

Cain, for his part, said his campaign has “no idea” who could be responsible for leaking the story. But he was unflappable about the accusations during his swing through D.C. on Monday.

“This flavour of the week is the flavour of the month and it still tastes good,” he said with a smile at a morning appearance to promote his 9-9-9 taxation plan.

But one political pundit says the sexual harassment allegations may continue to haunt Cain, no matter how forcefully he brushes them off, partly because he’s not a popular candidate among Republican women.

They largely prefer Romney, with 20 per cent of them saying in a recent poll they’d be “scared” if Cain won the nomination.

“The problem you have with new candidates who have come out of nowhere is that we don’t know them very well, so when things like this come up, they shape our opinion of a candidate,” said Ed Espinoza, a Democratic party consultant.

If Cain’s accusers actually come forward to provide more details, Espinoza said, his campaign would likely suffer a fatal blow. But even the suggestion that the women were paid off will likely be troubling to many Americans.

“When money is exchanged to make a problem go away, even though that might be standard operating procedure in the business world, people are invariably uncomfortable with that,” he said.

“In the court of public opinion, that seems to suggest there was something behind the allegations, and it just doesn’t go over very well.”